This invention provides an article comprising a vapor-deposited metal compound immobilized on a porous substrate. The invention also provides methods for depositing the metal compound. The article can also function as a catalyst for carbon-heteroatom coupling reactions such as carbon-carbon coupling reactions, most notably, the Heck reaction.
1. Background of the Invention
High-surface-area, porous substrates are of great interest in the field of catalysis. In particular, substrates with large and uniform pore sizes allow sterically-hindered molecules easy diffusion to internal active sites. Typically, catalytic species are immobilized within pores of porous substrates by depositing a catalyst from solution within pores of the substrate. In general, it is a challenge in the art to provide good deposition techniques for secure immobilization of catalysts on porous substrates, and the fabrication of substrates having large pore sizes has in many cases been challenging. It is among the objects of the present invention to provide techniques for secure immobilization of species on porous substrates, articles produced thereby, and methods of reactive chemistry using such articles.
2. Discussion of Related Art
U.S. Pat. No. 5,391,528 (Benazzi, et al.) describe deposition, from vapor, from organometallic compounds onto alumino-silicates.
U.S. Pat. No. 5,641,723 (Bonnemann, et al.) describe a technique for preparing highly-active doped supported catalysts from an organic or inorganic support material and a catalyst metal precursor. Deposition occurs from solution phase.
The invention provides methods of making surface-immobilized, metal-based catalysts, articles that can be useful for catalyzing organic reactions, and catalytic reactions involving metal-based catalysts.
According to one aspect, the invention involves methods of making articles. One method involves volatilizing an inorganic compound, and allowing the inorganic compound to become immobilized on a porous oxygen-containing substrate. The immobilization occurs to the extent that it is immobilized under sublimation conditions.
Another method of the invention involves pretreating a substrate having a plurality of chemically active sites of a first chemical functionality such that about 1-25% of the sites retain the first chemical functionality and about 75-99% of the sites have a second functionality. The sites retaining the first chemical functionality are uniformly dispersed. An inorganic compound then is volatilized to cause it to covalently bond to the pretreated substrate.
Another method of the invention involves providing a porous substrate having an average pore size of at least about 8 xc3x85 and depositing a metal compound on the substrate. Then, a carbon-heteroatom coupling reaction is carried out involving the metal compound.
Another method of the invention involves performing a carbon-heteroatom coupling reaction in air, wherein at least about 5% conversion, of the reaction, is achieved within about 1 h.
Another method of the invention involves carrying out a reaction catalyzed by a surface-immobilized catalyst having a surface area of at least about 50 m2/g, in air, at a temperature of at least about 50xc2x0 C. Catalyst degradation, defined by reduction of activity of catalysts, is allowed in an amount of less than about 30% of a period of time of at least about 1 h.
In another aspect the invention involves compositions and articles. One composition of the invention comprises the structure SUBSTRATExe2x80x94Oxe2x80x94Mxe2x80x94Lx, wherein a bond between O and M is a covalent bond.
In another embodiment an article is provided that comprises a vapor-deposited metal compound immobilized on a porous substrate. The substrate has an average pore size of at least about 8 xc3x85.